Several nomenclatures are important:

●Nuclide: is any particular atomic nucleus with a specific atomic number Z and mass number A, it is equivalently an atomic nucleus with a specific number of protons and neutrons. Nuclides may be stable or unstable and unstable nuclides are radioactive.

● ●Isotopes:Isotopes: is one series of nuclides have the same atomic number, but a is one series of nuclides have the same atomic number, but a different number of neutrons. They exhibit the same chemical propertiesdifferent number of neutrons. They exhibit the same chemical properties..

Examples Examples : : A carbon atom: It has 6 protons and 6 neutrons we call it A carbon atom: It has 6 protons and 6 neutrons we call it ʺcarbon-12“ ʺcarbon-12“ 1212

66C because it has an atomic mass of 12. One useful isotope C because it has an atomic mass of 12. One useful isotope

of carbon is ʺcarbon-14“, of carbon is ʺcarbon-14“, 141466C which has 6 protons and 8 neutronsC which has 6 protons and 8 neutrons..

Another example is the oxygen isotopes Another example is the oxygen isotopes 151588O, O, 1616

88O, O, 171788O, O, 1818

88OO..

Comparison of Two IsotopesComparison of Two Isotopes

● ●Isotones:Isotones: nuclides having the same number of neutrons but different nuclides having the same number of neutrons but different atomic number. Example, atomic number. Example, 5959

2626Fe, Fe, 60602727Co, Co, 6262

2929Cu each having 33 neutrons.Cu each having 33 neutrons.

● Isobars:Isobars: nuclides with the same mass number, but different number of nuclides with the same mass number, but different number of protons and neutrons, example protons and neutrons, example 6767

2929Cu, Cu, 67673030Zu are isobars having the same Zu are isobars having the same

mass number 67.mass number 67.

●● Isomers: Isomers: nuclides having the same number of protons and neutrons but nuclides having the same number of protons and neutrons but differing in energy states. Example differing in energy states. Example 9999Tc and Tc and 99m99mTc.Tc.

The nuclides, both stable and radioactive are arranged in the form of a The nuclides, both stable and radioactive are arranged in the form of a chartchart..

Comparison of Two IsobarsComparison of Two Isobars

Comparison of Two IsomersComparison of Two Isomers  

""Chart of NuclidesChart of Nuclides""

Radioisotopes, Radionuclides: Radioisotopes, Radionuclides: unstable isotopes which are unstable isotopes which are distinguishable by radioactive transformationdistinguishable by radioactive transformation..

Radioactivity:Radioactivity: the process in which an unstable isotope undergoes the process in which an unstable isotope undergoes changes until a stable state is reached and in the transformation emits changes until a stable state is reached and in the transformation emits energy in the form of radiation (alpha particles, beta particles and energy in the form of radiation (alpha particles, beta particles and gamma rays)gamma rays)..

RadiationRadiation refers to particles or waves coming from the nucleus of the refers to particles or waves coming from the nucleus of the atom atom (radioisotope or radionuclide)(radioisotope or radionuclide) through which the atom attempts through which the atom attempts to attain a more stable configurationto attain a more stable configuration..

Electron voltElectron volt::11 eV is the energy acquired by an electron when accelerated through a eV is the energy acquired by an electron when accelerated through a

potential difference of 1 Vpotential difference of 1 V . .This amount of energy is very small, so the energies of particles are This amount of energy is very small, so the energies of particles are usually given in terms of: MeV (megaelectron volt)usually given in terms of: MeV (megaelectron volt)

KeV (kiloelectron volt)KeV (kiloelectron volt) 11 MeV = 10MeV = 103 3 KeV = 10KeV = 106 6 eVeV

Nuclear stabilityNuclear stability

The stability of the atoms depends (N/Z) ratio in the nucleus.

Above the atomic number 82, all elements are radioactive.

The nucleons (P or N) are in a state of continual motion (natural isotopes)

If additional N or a deficiency of N occurs, the atom attempts to regain its stability by giving off either a photon, such as gamma ray, or particle from the nucleus to attain a more stable (N/Z) ratio and the nucleus is transformed into another.

This phenomenon is known as radioactivity or radioactive decay

Radioactive decayRadioactive decay Majority of nuclides are unstable and the unstable nuclei decay by spontaneous fission, α-particle, β-particle, or γ-ray emission or electron capture in order to achieve stable.

The radio-nuclides decay to achieve the N/Z ratio of the nearest possible stable nuclide. Radioactive decay by particle emission or electron capture changes the atomic number. Radionuclides may decay by any one or a combination of five process α decay, β- decay, β+decay, electron capture or isomeric transition.

Radioactive decayRadioactive decay

Mode of radioactive decay:

Radioactive decayIs the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation.

This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter nuclide.

When an unstable nucleus decays, It may give out-:

Modes of nuclear decay

Alpha decayα-emission

Beta decay

Negatronβ- emission

Positronβ+ emission

Electron capture Nuclear fission Gamma emission Isomeric transition

11 . .Alpha particle decay (Alpha particle decay (αα-decay):-decay):

● ● αα-decay occurs in very heavy elements, for example, -decay occurs in very heavy elements, for example, Uranium (U) and Uranium (U) and Radium (Ra). Radium (Ra).

●● Alpha particles are made ofAlpha particles are made of 2 protons and 2 neutrons 2 protons and 2 neutrons bound together in bound together in the nucleus.the nucleus. We can write them as We can write them as 44

22αα , or , or 4422He, because they're the same He, because they're the same

as a helium nucleus.as a helium nucleus.

● ● This means that when a nucleus emits an alpha particle, its atomic This means that when a nucleus emits an alpha particle, its atomic number decreases by 2 and its atomic mass decreases by 4. number decreases by 2 and its atomic mass decreases by 4. Example: Example: 235235

9292U U 2312319090Th + Th + 44

22HeHe

● Alpha particles are relatively ● Alpha particles are relatively slowslow and and heavy.heavy.●● Alpha particles emitted from a particular nuclide have the same Alpha particles emitted from a particular nuclide have the same energyenergy..

αα- Decay (- Decay (αα- emission)- emission)

They have a They have a low penetrating powerlow penetrating power - you can stop them with just a sheet of paper. - you can stop them with just a sheet of paper.

Because they have a large charge, alpha particles ionize other atoms strongly Because they have a large charge, alpha particles ionize other atoms strongly..

Since alpha particles cannot penetrate the dead layer of the skin, they do not present a hazard from  exposure external to the body .

However, due to the very large number of ionizations they produce in a very short distance, alpha emitters can present a serious hazard when they are in close proximity to cells and tissues such as the lung. Special precautions are taken to ensure that alpha

emitters are not inhaled, ingested or injected.

22 - -Beta particle decay (Beta particle decay (ββ-decay):-decay):

● ● Beta particles have a charge of Beta particles have a charge of minus 1minus 1. This means that beta particles . This means that beta particles are are the same as an electron. the same as an electron. We can write them as We can write them as ββ- - or eor e--, because they're the same as an electron., because they're the same as an electron.

A. Negatron (A. Negatron (ββ-- ) emission: ) emission: Nuclei with excess neutrons gain stability by conversion of a neutron Nuclei with excess neutrons gain stability by conversion of a neutron into a (proton + into a (proton + ββ- - + + vv). ). vv is an antineutrino which is needed to conserve is an antineutrino which is needed to conserve energy in the decay.energy in the decay. There is no change in the mass number, but the atomic number There is no change in the mass number, but the atomic number increases by one unit.increases by one unit.Example of Example of ββ- - decay:decay:131131

5353I I 1311315454Xe + Xe + ββ- - + + vv generally: n → p +β-+ v

Negatron (Negatron (ββ-- ) emission ) emission::

4019K 40

20Ca + β- + antineutrino

B. Positron or B. Positron or ββ++ Decay: Decay:

This process occur with This process occur with neutron deficientneutron deficient or or proton richproton rich nuclei. nuclei.

Conversion of a proton into neutron + positron ( Conversion of a proton into neutron + positron (ββ++ ) + ) + v v (neutrino).(neutrino).

Positrons are emitted with a continuous energy spectrum. Positrons are emitted with a continuous energy spectrum.

After After ββ++ particle emission, the daughter nuclide has an atomic number particle emission, the daughter nuclide has an atomic number that is one less than that of the parent.that is one less than that of the parent.

There is no change in the mass number but the atomic number is There is no change in the mass number but the atomic number is reduced by one unit.reduced by one unit.

Examples:Examples:6464

2929Cu → Cu → 64642828Ni + Ni + ββ++ + + vv

151588O → O → 1515

77N + N + ββ++ + + vv

generally: p → n + β+ + v

●● They are They are fast, and light. fast, and light. ●● Beta particles have a Beta particles have a medium penetrating powermedium penetrating power - they are stopped by - they are stopped by a sheet of aluminium.a sheet of aluminium.●● Beta particles ionize atoms that they pass, but not as strongly as alpha Beta particles ionize atoms that they pass, but not as strongly as alpha particles doparticles do..

Beta particles are much less massive and less charged than alpha particles and interact less intensely with atoms in the materials they pass through, which gives them a longer range than alpha particles.

33 . .Gamma-emission (Gamma-emission (γγ rays): rays):

● ● Gamma rays are waves, not particles. Gamma rays are waves, not particles. ● This means that they have ● This means that they have no mass and no charge. no mass and no charge. ●● In Gamma decay: atomic number unchanged, atomic In Gamma decay: atomic number unchanged, atomic mass unchanged.mass unchanged.

● ● Gamma rays have Gamma rays have a high penetrating powera high penetrating power - it takes - it takes a thick sheet of metal such as lead to reduce them.a thick sheet of metal such as lead to reduce them.

● Gamma rays do not directly ionize other atoms, ● Gamma rays do not directly ionize other atoms, although they may cause atoms to emit other particles although they may cause atoms to emit other particles which will then cause ionization.which will then cause ionization.

● We don't find pure gamma sources - gamma rays are ● We don't find pure gamma sources - gamma rays are

emitted alongside alpha or beta particlesemitted alongside alpha or beta particles..

Gamma radiationGamma radiation

Alpha particles are easy to stop, gamma Alpha particles are easy to stop, gamma rays are hard to stoprays are hard to stop . .

Mode of radioactive decayMode of radioactive decay::

Type of RadiationType of Radiation Alpha Alpha particleparticle

Beta particleBeta particle Gamma rayGamma ray

SymbolSymbol oror

ChargeCharge ++22 --1100

SpeedSpeed slowslowfastfastVery fastVery fast

Ionising abilityIonising ability highhighmediummedium00

Penetrating Penetrating powerpower

lowlowmediummediumhighhigh

Stopped byStopped by:: paperpaper aluminiumaluminiumleadlead

23492U 230

90Th

Determine whether alpha or beta decay occurs in the reaction in Determine whether alpha or beta decay occurs in the reaction in which lead-210 decays to bismuth-210.which lead-210 decays to bismuth-210.

2102108282Pb Pb 210210

8383Bi + Bi + AAZZXX

Negatron decay β-2102108282Pb Pb 210210

8383Bi +Bi + 0 0-1-1ββ

Identify the decay particle emitted and the decay process that occurs when protactinium-231 decays to actinium-227.

23191Pa 227

89Ac + AZX

23191Pa 227

89Ac + 42He Alpha (α)-decay